One example of a known conventional sealing device provided with a floating ring is illustrated in FIG. 6 (hereinafter referred to as the first prior art; for example, see Patent Document 1). In the first prior art, a floating ring 30 has a low-pressure-side surface which is in contact with an engaging ring 32 provided to a casing and to which is provided a pressure balance groove 33 for guiding a high-pressure fluid, the pressure balance groove being constituted of at least one circumferential groove as well as a plurality of rectilinear grooves extending in an outer peripheral direction from the circumferential groove. A wedging effect is thereby generated at a small portion in a gap formed between a rotating shaft 31 and an inner peripheral surface of the floating ring 30 (the effect of dynamic pressure generated at a wedge part), and the wedging effect is employed to fully bring about a self-aligning action aimed at maintaining a uniform gap between the rotating shaft 31 and the inner peripheral surface of the floating ring 30, as well as to: hinder any deformation of the floating ring 30; keep constant the gap between the rotating shaft 31 and the inner peripheral surface of the floating ring 30; prevent damage to the floating ring 30, caused by there being contact between the inner peripheral surface of the floating ring 30 and the rotating shaft 31 in motion; and prevent any increase in the amount of high-pressure fluid leaking out to the low-pressure side and/or prevent the equipment from discontinuing operation.
A different example of another known conventional sealing device provided with a floating ring is illustrated in FIG. 7 (hereinafter referred to as the second prior art; for example, see Patent Document 2). In the second prior art, interconnecting parts 36 oriented radially outward are provided to an outer periphery of a floating ring 35 formed in an annular shape; the interconnecting parts 36 are provided as a pair at 180° intervals in the circumferential direction and are inserted into a groove part 38 of a casing 37, thus supporting the floating ring 35 in a manner concentric with a rotating shaft 39.
However, in the sealing device provided with the floating ring in the first prior art illustrated in FIG. 6, although an advantage is presented in that the self-aligning action aimed at keeping uniform the gap formed between the rotating shaft 31 and the inner peripheral surface of the floating ring 30 is brought about, no turn-stopping means is provided for the floating ring 30, and therefore in a case such as where the rotational speed of the rotating shaft 31 becomes higher, a problem has been presented in that the influence of a viscous fluid interposed in the gap between the floating ring 30 and the rotational shaft 31 causes the floating ring 30 to rotate, and causes the behavior of the floating ring 30 to become unstable. Further, in the sealing device provided with the floating ring in the first prior art, in a case where the dynamic pressure generated at the small portion in the gap between the rotating shaft 31 and the inner peripheral surface of the floating ring 30 is less than the weight of the floating ring 30, then operation will thus take place in a state where the gap formed between the rotating shaft 31 and the inner peripheral surface of the floating ring 30 ceases to be uniform and becomes eccentric.
In the sealing device provided with the floating ring in the second prior art illustrated in FIG. 7, the floating ring 35 will not rotate, because the pair of interconnecting parts 36 provided at a 180° interval in the circumferential direction are inserted into the groove part 38 of the casing 37. However, in practice, it is difficult to assemble the floating ring 35 to be concentric with the rotating shaft 39, and therefore a problem is presented in that the floating ring 35 is assembled in an eccentric state relative to the rotating shaft 39. An additional problem has been presented in that the floating ring 35 is unable to flexibly track the eccentricity of the rotating shaft 39 caused by the deflection of the rotating shaft 39 or a similar factor.